Salt suitable for an acid generator and a chemically amplified resist composition containing the same

ABSTRACT

The present invention provides a salt of the formula (I): 
                         
wherein ring X represents monocyclic or bicyclic hydrocarbon group having 3 to 30 carbon atoms, and one or more hydrogen atom in the ring X is optionally substituted with alkyl group having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6 carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q 1  and Q 2  each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A +  represents organic counter ion; and n shows an integer of 1 to 12.
 
     The present invention also provides a chemically amplified resist composition comprising the salt of the formula (I).

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2005-314038 filed in JAPAN on Oct. 28, 2005,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt suitable for an acid generatorused for a chemical amplification type resist which is used in fineprocessing of semiconductors, and a chemically amplified resistcomposition containing the salt.

BACKGROUND OF THE INVENTION

A chemically amplified resist composition used for semiconductormicrofabrication employing a lithography process contains an acidgenerator comprising a compound generating an acid by irradiation.

In semiconductor microfabrication, it is desirable to form patternshaving high resolution and excellent pattern shape, and it is ex for achemically amplified resist composition to give such patterns.

Recently, a chemically amplified resist composition containingtriphenylsulfonium 1-adamantanemethoxylcarbonyldifluoromethansulfonate,p-tolyldiphenylsiifoniuin perfluorooctanesulfonate, and the like areproposed (e.g. JP2004-4561-A), and a salt providing a chemicallyamplified resist composition giving patterns having higher resolutionand more excellent pattern shape.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a salt suitable for anacid generator capable of providing chemically amplified resistcompositions giving patterns having high resolution and excellentpattern shape.

Another objects of the present invention are to provide syntheticintermediates for the salts and to provide a process for producing thesynthetic intermediates or the salts.

Still another object of the present invention are to provide achemically amplified resist composition containing the salts.

These and other objects of the present invention will be apparent fromthe following description.

The present invention relates to the followings:

<1> A salt of the formula (I):

wherein ring X represents monocyclic or bicyclic hydrocarbon grouphaving 3 to 30 carbon atoms, and one or more hydrogen atom in the ring Xis optionally substituted with alkyl group having 1 to 6 carbon atoms;alkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q¹ andQ² each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and nshows an integer of 1 to 12. Hereinafter, the salt of the formula (I)may also be referred to as Salt (I).

<2> The salt according to <1>, wherein the ring X is monovalent residueof a compound shown by the formula (IIIa), (IIIb), (IIIc), (IIId),(IIIe) or (IIIf):

wherein X¹ represents alkylene group, oxygen atom or sulfur atom and oneor more hydrogen atom in the formulae (IIIa), (IIIb), (IIIc), ((IIId),(IIIe) and (IIIf) is optionally substituted with alkyl group having 1 to6 carbon atoms, alkoxy group having 2 to 6 carbon atoms orperfluoroalkyl group having 1 to 4 carbon atoms, and f shows an integerof 1 to 10.

<3> The salt according to <1> or <2>, wherein the ring X is cyclohexylgroup or bicyclo[2.2.1]heptyl group.

<4> The salt according to any of <1> to <3>, wherein A⁺ is at least onecation selected from the group consisting of the formula (IIe), theformula (IIb), the formula (IIc) and the formula (IId);

a cation of the formula (IIe):

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms, a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl group having 1 to12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P⁶and P⁷ bond to form divalent acyclic hydrocarbon group having 3 to 12carbon atoms which forms a ring together with the adjacent S⁺, and oneor more —CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12carbon atoms or aromatic ring group optionally substituted, or P⁸ and P⁹bond to form divalent acyclic hydrocarbon group which forms2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂—in the divalent acyclic hydrocarbon group is optionally substituted with—CO—, —O— or —S—, a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m shows 0 or 1.

<5> The salt according to <4>, wherein the cation of the formula (IIe)is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms and l, k,j, i, h and g each independently show an integer of 0 to 5.

<6> The salt according to <4>, wherein the cation of the formula (IIe)is a cation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.

<7> The salt according to <6>, wherein the cation of the formula (IIa)is a cation of the formula (IIi):

wherein P²², P²³ and P³⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.

<8> The salt according to claim 1, wherein the salt is a salt of theformula (IV) or (V)

P²², P²³ and P²⁴ have the same meanings as defined above.

<9> The salt according to any of <1> to <8>, wherein each of Q¹ and Q²is independently fluorine atom or trifluoromethyl group.

<10> An ester compound of the formula (VI)

wherein X represents monocyclic or bicyclic hydrocarbon group having 3to 30 carbon atoms, and one or more hydrogen atom in the ring X isoptionally substituted with alkyl group having 1 to 6 carbon atoms,alkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q¹ andQ² each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; M represents Li, Na, K or Ag; and n shows aninteger of 1 to 12.

<11> A process for producing an ester compound of the formula (VI),which comprises reacting an alcohol compound of the formula (VII)

wherein X and n have the same meanings as defined above,with a carboxylic acid compound of the formula (VIII)

wherein M, Q¹ and Q² have the same meaning as defined above.

<12> A process for producing Salt (I)

which comprises reacting an ester compound of the formula (VI) with acompound of the formula (IX)A⁺ Z⁻  (IX)wherein Z represents F, Cl, Br, I, BF₄, AsF₆, PF₆ or ClO₄, and A⁺ hasthe same meaning as defined above.

<13> A chemically amplified resist composition comprising Salt (I) and

a resin which contains a structural unit having an acid-labile group andwhich itself is insoluble or poorly soluble in an alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid.

<14>. The composition according to <13>, wherein the resin contains astructural unit derived from a monomer having a bulk and acid-labilegroup.

<15> The composition according to <14>, wherein the bulky andacid-labile group is 2-alkyl-2-adamantyl group or1-(1-adamantyl)-1-alkylalkyl group.

<16> The composition according to <14>, wherein the monomer having bulkyand acid-labile group is 2-alkly-2-adamantyl (meth)acrylate,1-(-1-adamantyl)-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl5-norbornene-2-carboxylate, 2-alkyl-2-adamantyl α-chloroacrylate or1-(-1-adamantyl)-1-alkylalkyl α-chloroacrylate.

<17>

The composition according to any of <13> to <16>, wherein thecomposition further comprises a basic compound.

<18> The composition according to any of <13> to <17>, wherein each ofQ¹ and Q² is independently fluorine atom or trifluoromethyl group.

<19> The composition according to any of <13> to <18>, wherein the ringX is monovalent residue of a compound shown by the formula (IIIa),(IIIb), (IIIc), ((IIId), ((IIIe) or (IIIf).

<20> The composition according to any of <13> to <19>, wherein the ringX is cyclohexyl group or bicyclo[2.2.1]heptyl group.

<21> The composition according to any of <13> to <20>, wherein A⁺ is atleast one cation selected from the group consisting of the formula(IIe), the formula (IIb), the formula (IIc) and the formula (IId).

<22> The composition according to <21>, wherein the cation of theformula (IIe) is a cation of the formula (IIf), (IIg) or (IIh).

<23> The composition according to <21>, wherein the cation of theformula (IIe) is a cation of the formula (IIa).

<24> The composition according to <23>, wherein the cation of theformula (IIa) is a cation of the formula (IIi).

<25> The composition according to any of <13> to <17>, wherein the saltis a salt of the formula (IV) or (V).

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides Salt (I).

The ring X in the formulae (I), (VI) and (VII) represents monocyclic orbicyclic hydrocarbon group and has 3 to 30, preferably 3 to 12 carbonatoms. “n” shows an integer of 1 to 12, and preferably 1 to 4. One ormore hydrogen atom in the ring X is optionally substituted with alkylgroup having 1 to 6 carbon atoms, alkenyl group having 2 to 6 carbonatoms, alkoxy group having 2 to 6 carbon atoms or perfluoroalkyl grouphaving 1 to 4 carbon atoms.

It is preferred that the ring X include monovalent residue of a compoundshown by the formula (IIIa), (IIIb), (IIIc), (IIId), (IIIe) or (IIIf).

X¹ represents akylene group such as methylene group and ethylene group,oxygen atom (—O—) or sulfer atom (—S—). “f” shows an integer of 1 to 10and preferably 1 to 6.

Specific examples of the compound of the formulae (IIIa), (IIIb),(IIIc), (IIId), (IIIe) and (IIIf) include the followings:

“n” is 1 to 12, and preferably 1 to 4.

Q¹ and Q² each independently represent fluorine atom or perfluoroalkylgroup having 1 to 6 carbon atoms such as trifluoromethyl group,pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group,undecafluoropentyl group, tridecafluorohexyl group, and the like. As Q¹and Q², fluorine atom and trifluoromethyl group are preferred.

Specific examples of anion part of the Salt (I) include the followings:

A⁺ in the formulae (I) and (VIII) represents organic counter ion.Examples thereof include the cations of the formulae (IIe), (IIb), (IIc)and (IId),

In the cation of the formula (IIe), P²⁵, P²⁶ and P²⁷ each independentlyrepresent alkyl group having 1 to 30 carbon atoms or cyclic hydrocarbongroup having 3 to 30 carbon atoms. One or more hydrogen atom in thealkyl group in the formula (IIe) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms and one or more hydrogen atom in thecyclic hydrocarbon group in the formula (IIe) is optionally substitutedwith hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxygroup having 1 to 12 carbon atoms.

Examples of the alkyl group in the formula (IIe) include methyl group,ethyl group, propyl group, isopropyl group, n-butyl group, sec-butylgroup, tert-butyl group, pentyl group, hexyl group, octyl group,2-ethylhexyl group, and the like, and examples of the alkoxy groupinclude methoxy group, ethoxy group, propoxy group, butoxy group,hexyloxy group, octyloxy group, 2-ethylhexyloxy group, and the like.Examples of the cyclic hydrocarbon group include cyclopentyl group,cyclohexyl group, adamantyl group, bicyclohexyl group, phenyl group,naphtyl group, fluorenyl group, biphenyl group, and the like.

In the cation of the formula (IIe), cations of the formulae (IIf), (IIg)and (IIh) are preferred. In the cations of the formulae (IIf), (IIg) and(IIh), P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group. One or more hydrogen atom in the alkyl group in theformulae (IIf), (IIg) and (IIh) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms. One or more hydrogen atom in thecyclic hydrocarbon group in the formulae (IIf), (IIg) and (IIh) isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group, alkoxy group and cyclic hydrocarbon group include thesame groups as mentioned in the formula (IIe) above.

P³¹, P³² P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxylgroup, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to12 carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms,and l, k, j, i, h and g each independently show an integer of 0 to 5.Examples of the alkyl group, alkoxy group and cyclic hydrocarbon groupinclude the same groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIe), the one of the formula (IIa) is morepreferred. In the cation of the formula (IIa), P¹, P² and P³ eachindependently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms.

Examples of the alkyl group and alkoxy group in the formula (IIa)include the same groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIa), the one of the formula (IIi) aboveis preferred for the easiness of production.

In the cation of the formula (IIb), P⁴ and P⁵ each independentlyrepresent hydrogen atom, hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group and alkoxy group include the same groups as mentioned inthe formula (IIe) above.

In the cation of the formula (IIc), P⁶ and P⁷ each independentlyrepresent alkyl having 1 to 12 carbon atoms or cycloalkyl having 3 to 12carbon atoms, or P⁶ and P⁷ bond to form divalent acyclic hydrocarbongroup having 3 to 12 carbon atoms which forms a ring together with theadjacent S⁺, and at least one —CH₂— in the divalent acyclic hydrocarbonmay be substituted with —CO—, —O— or —S—.

P⁸ represents hydrogen, P⁹ represents alkyl having 1 to 12 carbon atoms,cycloalkyl having 3 to 12 carbon atoms or aromatic ring group optionallysubstituted, or P⁸ and P⁹ bond to form divalent acyclic hydrocarbongroup which forms 2-oxocycloalkyl together with the adjacent —CHCO—, andone or more —CH₂— in the divalent acyclic hydrocarbon group isoptionally substituted with —CO—, —O— or —S—.

In P⁶, P⁷ and P⁹, specific examples of the alkyl group include methylgroup, ethyl group, propyl group, isopropyl group, butyl group,tert-butyl group, pentyl group, hexyl group, and the like, and specificexamples of the cycloalkyl group include cyclopropyl group, cyclobutylgroup, cyclopentyl group, cyclohexyl group, cycloheptyl group,cyclodecyl group, and the like. Specific examples of the divalentacyclic hydrocarbon group having 3 to 12 carbon atoms formed by bondingP⁶ and P⁷ include trimethylene group, tetramethylene group,pentamethylene group, and the like, and specific examples of the ringgroup formed by acjacent S⁺ and divalent acyclic hydrcarbon group by P⁶and P⁷ include pentamethylenesulfonio group, tetramethylenesulfoniogroup, oxybisethylenesulfonio group, and the like. In P⁹, specificexamples of the aromatic ring group include phenyl, tolyl, xylyl,naphtyl and the like. Specific examples of the divalent acyclichydrocarbon group formed by bonding P⁸ and P⁹ include methylene group,ethylene group, trimethylene group, tetramethylene group, pentamethylenegroup, and the like, and specific examples of the 2-oxocycloalkyl formedby bonding P⁸ and P⁹ together with the adjacent —CHCO— include2-oxocyclohexyl, 2-oxocyclopentyl and the like.

In the cation of the formula (IId), P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶,P¹⁷, P¹⁸, P¹⁹, P²⁰, and P²¹ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom,and m represents 0 or 1. Examples of the alkyl group and alkoxy groupinclude the same groups as mentioned in the formula (IIe) above.

As A⁺, at least one cation selected from the group consisting of thecations of the formulae (IIf), (IIg), (IIh), (IIb), (IIc) and (IId) ispreferred, and at least one cation selected from the group consisting ofthe cations of the formulae (IIa), (IIb), (IIc) and (IId) is alsopreferred. As A⁺, the cation of the formula (IIi) is more preferred.

Specific examples of the cation of the formula (IIe) include thefollowing:

Specific examples of the formula (IIb) include the following:

Specific examples of the formula (IIc) include the following:

Specific examples of the cation of the formula (IId) include thefollowing:

As Salt (I), the salt of the formulae (IV) and (V) is preferred forproviding chemically amplified resist compositions giving patternshaving higher resolution and more excellent pattern shape.

Examples of a process for production of Salt (I) include a processcomprising reacting an ester of the formula (VI) with the compound ofthe formula (IX), in an inert solvent such as acetonitrile, water,methanol, chloroform and dichloromethane at a temperature of 0 to 150°C., preferably of 0 to 100° C.

The amount of the compound of the formula (IX) is usually 0.5 to 2 molper 1 mol of the ester of the formula (VI). Salt (I) obtained can betaken out by recrystallization when it is in crustal form or byextraction by solvents and concentration when it is in oil form.

Examples of a process for production of the ester of the formula (VI)include a process reacting an alcohol compound of the formula (VII) witha carboxylic acid compound of the formula (VIII).

The esterification reaction can generally be carried out by mixingmaterials in an aprotic solvent such as dichloroethane, toluene,ethylbenzene, monochlorobenzene, acetonitrile, N,N dimethylformamide,and the like, at 20 to 200° C., preferably 50 to 150° C. In theesterification reaction, an acid catalyst or a dehydrating agent isusually added, and examples of the acid catalyst include organic acidssuch as p-toluenesulfonic acid, inorganic acids such as sulfuric acid,and the like. Examples of the dehydrating agent include1,1′-bonyldiimidazole, N,N′-dicyclohexylcarbodiimide, and the like.

The esterification may preferably be carried out with dehydration, forexample, by Dean and Stark method as the reaction time tends to beshortened.

The amount of the carboxylic acid compound of the formula (VIII) isusually 0.2 to 3 mol, preferably 0.5 to 2 mol per 1 mol of the alcoholcompound of the formula (VII). The amount of the acid catalyst may becatalytic amount or the amount equivalent to solvent, and is usually0.001 to 5 mol per 1 mol of the alcohol compound of the formula (VII).The amount of the dehydrating agent is usually 0.2 to 5 mol, preferably0.5 to 3 mol per 1 mol of the alcohol compound of the formula (VII).

The present chemically amplified resist composition comprises Salt (I)and a resin which contains a structural unit having an acid-labile groupand which itself is insoluble or poorly soluble in an alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid.

Salt (I) is usually used as an acid generator, and the acid generated byirradiation to Salt (I) catalytically acts against acid-labile groups ina resin, cleaves the acid-labile-group, and the resin becomes soluble inan alkali aqueous solution. Such a composition is suitable forchemically amplified positive resist composition.

The resin used for the pet composition contains a structural unit havingan acid-labile group and which itself is insoluble or poorly soluble inan alkali aqueous solution, but acid-labile group cleave by an acid. Theresin after the cleavage contains carboxylic acid residue and as aresult, the resin becomes soluble in an alkali aqueous solution.

In the present specification, “—COOR” may be described as “a structurehaving ester of carboxylic acid”, and may also be abbreviated as “estergroup”. Specifically, “—COOC(CH₃)₃” may be described as “a structurehaving tert-butyl ester of carboxylic acid”, or be abbreviated as“tert-butyl ester group”.

Examples of the acid-labile group include a structure having ester ofcarboxylic acid such as alkyl ester group in which a carbon atomadjacent to the oxygen atom is quaternary carbon atom, and alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, and the like, a lactone ring group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom, andthe like.

The “quaternary carbon atom” means a “carbon atom joined to foursubstituents other than hydrogen atom”.

Examples of the acid-labile group include alkyl ester group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom suchas tert-butyl ester group; acetal type ester group such as methoxymethylester group, ethoxymethyl ester group, 1-ethoxyethyl ester group,1-isobutoxyethyl ester group, 1-isopropoxyethyl ester group,1-ethoxypropyl ester group, 1-(2-methoxyethoxy)ethyl ester,1-(2-acetoxyethoxy)ethyl ester group, 1-[2-(1-adamantyloxy)ethoxy]ethylester group, 1-[2-1-adamtanecarbonyloxy)ethoxy]ethyl ester group,tetrahydro-2-furyl ester and tetrahydro-2-pyranyl ester group; alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, such as isobornyl ester group, 1-alkylcycloalkylester group, 2-alkyl-2-adamantyl ester group,1-(1-adamantyl)-1-alkylalkyl ester group, and the like.

Examples of structures including the ester group include ester of(meth)acrylic acid structure, ester of norbornenecarboxylic acidstructure, ester of tricyclodecenecarboxylic acid stucture,tetracyclodecenecarboxylic acid structure, and the like. At least onehydrogen atom in the adamantyl group above may be substituted byhydroxyl group.

The resin used for the present composition can be obtained by additionpolymerization of monomer(s) having an acid-labile group and olefinicdouble bond.

Among the monomers, it is preferable to use those having a bulky groupsuch as alicyclic group (e.g. 2-alkyl-2-adamantyl and1-(1-adamantyl)-1-alkylalkyl), as the group dissociated by the action ofan acid, since excellent resolution is obtained when used in the presentcomposition.

Examples of such monomer containing a bulky group include2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl(meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate,1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate,2-alkyl-2-adamantyl α-chloroacrylate, 1-(1-adamantyl)-1-alkylalkylα-chloroacrylate and the like.

Particularly when 2-alkyl-2-adamantyl (meth)acrylate or2-alkyl-2-adamantyl α-chloroacrylate is used as the monomer for theresin component in the present composition, resist composition havingexcellent resolution tend to be obtained. Typical examples of such2-alkyl-2-adamantyl (meth)acrylate and 2-alkyl-2-adamantylα-chloroacrylate include 2-methyl-2-adamantyl acrylate,2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate,2-ethyl-2-adamantyl methacrylate, 2-n-butyl-2-adamantyl acrylate,2-methyl-2-adamantyl α-chloroacrylate, 2-ethyl-2-adamantylα-chloroacrylate and the like. When particularly 2-ethyl-2-adamantyl(meth)acrylate or 2-isopropyl-2-adamantyl (meth)acrylate is used for thepresent composition, composition having excellent sensitivity and heatresistance tends to be obtained. In the present invention, two or morekind of monomers having group dissociated by the action of an acid maybe used together, if necessary.

2-Alkyl -2-adamantyl (meth)acrylate can usually be produced by reacting2-alkyl -2-adamantanol or metal salt thereof with an acrylic halide ormethacrylic halide.

The resin used for the present composition can also contain, in additionto the above-mentioned structural units having an aid-labile group,other structural unit derived from acid-stable monomer. Herein, the“structural unit derived from acid-stable monomer” means “a structuralunit not dissociated by an acid generated from Salt (I)”.

Examples of such other structural units which can be contained includestructural units derived from monomers having a free carboxyl group suchas acrylic acid and methacrylic acid, structural units derived fromaliphatic unsaturated dicarboxylic anhydrides such as maleic anhydrideand itaconic anhydride, structural units derived from 2-norbornene,structural units derived from (meth)acrylonitrile, structural unitsderived from alkyl (meth)acrylate in which a carbon atom adjacent tooxygen atom is secondary or tertiary carbon atom, structural unitsderived from 1-adamantyl (meth)acrylate, structural units derived fromstyrenes such as p- or m-hydroxystyrene, structural units derived from(meth)acryloyloxy-γ-butyrolactone having a lactone ring optionallysubstituted by alkyl, and the like. Herein, 1-adamantyl ester group is aacid-stable group though the carbon atom adjacent to oxygen atom is aquaternary carbon atom, and at least one hydrogen atom on 1-adamantyester group may be substituted by hydroxy group.

Specific examples of structural unit derived from acid-stable monomerinclude a structural unit derived from 3-hydroxyl-1-adamantyl(meth)acrylate, a structural unit derived from 3,5-dihydroxy-1-adamantyl(meth)acrylate, a structural derived fromα-(meth)acryloyloxy-γ-butyrolactone, a structural unit derived fromβ-(meth)acryloyloxy-γ-butyrolactone, a structural unit of the followingformula (a), a structural unit derived from the following formula (b), astructural unit derived from alicylic compound having olefinic doublebond such as a structural unit of the following formula (c), astructural unit derived from aliphatic unsaturated dicarboxylicanhydride such as a structural unit of the formula (d), a structuralunit of the formula (e), and the like.

Particularly, to contain, in addition to the structural unit having anacid-labile group, further at least one structural unit selected fromthe group consisting of a structural unit derived from p-hydroxystyrene,a structural unit derived from m-hydroxystyrne, a structural unitderived from 3-hydroxy-1-adamantyl (meth)acrylate, a structural unitderived from 3,5-dihydroxy-1-adamantyl (meth)acrylate, a structural unitof the following formula (a) and a structural unit of the followingformula (b), in the resin in the present composition, is preferable fromthe standpoint of the adhesiveness of resist to a substrate andresolution of resist.

In the formulae (a) and (b), R¹ and R² each independently representhydrogen atom, methyl group or trifluoromethyl group and R³ and R⁴ eachindependently represent methyl group, trifluoromethyl group or halogenatom, and p and q each independently represent an integer of 0 to 3.When p represents 2 or 3, each of the R³ may be the same or differentand when q represents 2 or 3, each of the R⁴ may be the same ordifferent.

3-Hydroxy-1-adamantyl (meth)acrylate and 3,5-dihydroxy-1-adamantyl(meth)acrylate can be produced, for example, by reacting correspondinghydroxyadamantane with (meth)acrylic acid or its acid halide, and theyare also commercially available.

Further, (meth)acryloyloxy-γ-butyrolactone having a lactone ringoptionally substituted by alkyl can be produced by reactingcorresponding γ- or β-bromo-γ-butyrolactone with acrylic acid ormethacrylic acid, or reacting corresponding α- orβ-hydroxy-γ-butyrolactone with acrylic halide or methacrylic halide.

As monomers to give structural units of the formulae (a) and (b),specifically listed are, for example, (meth)acrylates of alicycliclactones having hydroxyl described below, and mixtures thereof, and thelike. These esters can be produced, for example, by reactingcorresponding alicyclic lactone having hydroxyl with (meth)acrylicacids, and the production method thereof is described in, for example,JP2000-26446-A.

Examples of the (meth)acryloyloxy-γ-butyrolactone having a lactone ringoptionally substituted by alkyl include α-acryloyloxy-γ-butyrolactone,α-methacryloyloxy-γ-butyrolactone,α-acryloyloxy-β,β-dimethyl-γ-butyrolactone,α-methacryloyloxy-β,β-dimethly-γ-butyrolactone,α-acryloyloxy-α-methyl-γ-butyrolactone,α-methacryloyloxy-α-methyl-γ-butyrolactone,β-acryloyloxy-γ-butyrolactone, β-methacryloyloxy-γ-butyrolactone,β-methacryloyloxy-α-methyl-γ-butyrolactone and the like.

In the case of KrF lithography, even in the case of using a structureunit derived from hydroxystyrene such as p- and m-hydroxystyrene, as oneof the resin components, resist composition having sufficienttransparency can be obtained. For obtaining such copolymerizationresins, the corresponding (meth)acrylic ester monomer can beradical-polymerized with acetoxystyrene and styrene, and then theacetoxy group in the structure unit derived from acetoxystyrene can bede-acetylated with an acid.

The resin containing a structural unit derived from 2-norbornene showsstrong structure because alicycic group is directly present on its mainchain and shows a property that dry etching resistance is excellent. Thestructural unit derived from 2-norbornene can be introduced into themain chain by radical polymerization using, for example, in addition tocorresponding 2-norbornene, aliphatic unsaturated dicarboxylicanhydrides such as maleic anhydride and itaconic anhydride together. Thestructural unit derived from 2-norbornene is formed by opening of itsdouble bond, and can be represented by the formula (c). The structuralunit derived from maleic anhydride and the structural unit derived fromitaconic anhydride which are the structural unit derived from aliphaticunsaturated dicarboxylic anhydrides are formed by opening of theirdouble bonds, and can be represented by the formula (d) and the formula(e), respectively.

Here, R⁵ and R⁶ in the formula (c) each independently representhydrogen, alkyl having 1 to 3 carbon atoms, hydroxyalkyl having 1 to 3carbon atoms, carboxyl, cyano or —COOU group in which U representsalcohol residue, or R⁵ and R⁶ a bond together to form a carboxylicanhydride residue represented by —C(═O)OC(═O)—.

In R⁵ and R⁶, examples of the alkyl include methyl, ethyl, propyl andisopropyl, specific examples of hydroxyalkyl include hydroxymethyl,2-hydroxyethyl and the like.

In R⁵ and R⁶, —COOU group is an ester formed from carboxyl, and as thealcohol residue corresponding to U, for example, optionally substitutedalkyls having about 1 to 8 carbon atoms, 2-oxooxolan-3 or 4-yl and thelike are listed, and as the substituent on the alkyl, hydroxyl,alicyclic hydrocarbon residues and the like are listed.

Specific examples of the monomer used to give the structural unitrepresented by the formula (c) may include the following;

2-norbornene,

2-hydroxy-5-norbornene,

5-norbornen-2-carboxylic acid,

methyl 5-norbornen-2-carboxylate,

2-hydroxyethyl 5-norbornen-2-carboxylate,

5-norbornen-2-methanol,

5-norbornen-2, 3-dicarboxylic acid anhydride, and the like.

When U in —COOU is acid-labile group, the structural unit of the formula(c) is a structural unit having acid-labile group even if it hasnorbornene structure. Examples of monomers giving structural unit havingacid-labile group include t-butyl 5-norbornen-2-carboxylate,1-cyclohexyl-1-methylethyl 5-norbomen-2-carboxylate, 1-methylcyclohexyl5-norbornen-2-carboxylate, 2-methyl-2-adamantyl5-norbornen-2-carboxylate, 2-ethyl-2-adamantyl 5-norbomen-2-carboxylate,1-(4-methylcyclohexyl)-1-methylethyl 5-norbornen-2-carboxylate,1-(4-hydroxylcyclohexyl)-1-methylethyl 5-norbornen-2-carboxylate,1-methyl-1-(4-oxocyclohexyl)ethyl 5-norbornen-2-carboxylate,1-(1-adamanty)-1-methylethyl 5-norbornen-2-carboxylate, and the like.

The resin used in the present composition preferably contain structuralunit(s) having an acid-labile group generally in a ratio of 10 to 80% bymol in all structural units of the resin though the ratio variesdepending on the kind of radiation for patterning exposure, the kind ofan acid-labile group, and the like.

When the structural units particularly derived from 2-alkyl-2-adamantyl(meth)acrylate or 1-(1-adamantyl)-1-alkylalkyl (meth)acrylate are usedas the acid-labile group, it is advantageous in dry-etching resistanceof the resist that the ratio of the structural units is 15% by mol ormore in all structural unit of the resin.

When, in addition to structural units having an acid-labile group, otherstructural units having acid-stable group are contained, it ispreferable that the sum of these structural units is in the range of 20to 90% by mol based on all structural units of the resin.

When alicyclic compound having olefinic double bond and aliphaticunsaturated dicarboxylic anhydride are used as copolymerization monomer,it is preferable to use them in excess amount in view of a tendency thatthese are not easily polymerized.

In the present composition, performance deterioration caused byinactivation of acid which occurs due to post exposure delay can bediminished by adding basic compounds, particularly, basicnitrogen-containing organic compounds, for example, amines as aquencher.

Specific examples of such basic nitrogen-containing organic compoundsinclude the ones represented by the following formulae:

In the formula, T¹² and T¹³ each independently represent a hydrogenatom, an alkyl group, a cycloalkyl group or an aryl group. The alkylgroup preferably has about 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, and the aryl group preferablyhas about 6 to 10 carbon atoms. Furthermore, at least one hydrogen atomon the alkyl group, cycloalkyl group or aryl group may each independntlybe substituted with hydroxyl group, amino group, or alkoxy group having1 to 6 carbon atoms. At least one hydrogen atom on the amino group mayeach independently be substituted with alkyl group having 1 to 4 carbonatoms.

T¹⁴, T¹⁵ and T¹⁶ each independently represent a hydrogen atom, an alklylgroup, a cycloalkyl group, an aryl group or an alkoxy group. The alkylgroup preferably has about 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, the aryl group preferably hasabout 6 to 10 carbon atoms, and the alkoxy group preferably has about 1to 6 carbon atoms. Furthermore, at least one hydrogen atom on the alkylgroup, cyccloalkyl group, aryl group or alkoxy group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

T¹⁷ represents an alkyl group or a cycloalkyl group. The alkyl grouppreferably has about 1 to 6 carbon atoms, and the cycloalkyl grouppreferably has about 5 to 10 carbon atoms. Furthermore, at least onehydrogen atom on the alkyl group or cycloalkyl group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

In the formulas, T¹⁸ represents an alkyl group, a cycloalkyl group or anaryl group. The alkyl group preferably has about 1 to 6 carbon atoms,the cycloalkyl group preferably has about 5 to 10 carbon atoms, and thearyl group preferably has about 6 to 10 carbon atoms. Furthermore, atleast one hydrogen atom on the alkyl group, cycloalkyl group or arylgroup may each independently be substituted with a hydroxyl group, anamino group, or an alkoxy group having 1 to 6 carbon atoms. At least onehydrogen atom on the amino group may each independently be substitutedwith alkyl group having 1 to 4 carbon atoms.

However, none of T¹² and T¹³ in the compound represented by the aboveformula [3] is a hydrogen atom.

A represents alkylene group, carbonyl group, imino group, sulfide groupor disulfide group. The alkylene group preferably has about 2 to 6carbon atoms.

Moreover, among T¹²-T¹⁸, in regard to those which can be straigt-chainedor branched, either of these may be permitted.

T¹⁹, T²⁰ and T²¹ each independently represent a hydrogen atom, an alkylgroup having 1 to 6 carbon atoms, an aminoalkyl group having 1 to 6carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted aryl group having 6 to 20 carbon atoms, orT¹⁹ and T²⁰ bond to form an alkylene group which forms a lactam ringtogether with adjacent —Co—N—.

Examples of such compounds include hexylamine, heptylamine, octylamine,nonylamine, decylamine, aniline, 2-, 3- or 4-methylaniline,ethylenediamine, tetramethylenediamine, hexamethyleneddiamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, dibutylamine, dipentylamine,dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine,N-methylamine, piperidine, diphenylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethydipentylamine, ethyldhexylamine, ethydihepylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris[2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, N,N-dimethylamine, 2,6-isopropylaniline, pyridine,4-methylpyridine, bipyridine, 2,2′-dipyridylamine, di-2-pyridyl ketone,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethylene,1,2-bis(4-pyridyl)ethylene, 4,4′-dipyridyl sulfide, 4,4′-dipyridyldisulfide, 1,2-bis(pyridyl)ethylene, 2,2′-dipicolylamine,3,3′-dipicolylamine, tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetra-n-hexylammonium hydroxide, tetra-n-octylammonium hydroxide,phenyltrimethylammonium hydroxide,3-trifluoromethylphenyltrimethylammonium hydroxide,(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”),N-methylpyrrolidone, and the like.

Furthermore, hindered amine compounds having piperidine skeleton asdisclosed in JP-A-H11-52575 can be used as quencher.

It is preferable that the present composition contains resin componentin an amount of about 80 to 99.9% by weight and Salt (I) in an amount of0.1 to 20% by weight on the total amount of the resin component and Salt(I).

When basic compound is used as a quencher, the basic compound iscontained preferably in an amount of about 0.01 to 1 part by weight per100 parts by weight of sum of resin component and Salt (I).

The present composition can contain, if necessary, various additives insmall amount such as a sensitizer, solution suppressing agent, otherpolymers, surfactant, stabilizer, dye and the like, as long as theeffect of the present invention is not prevented.

The present composition is usually in the form of a resist liquidcomposition in which the aforementioned ingredients are dissolved in asolvent, and the resist liquid composition is to be applied onto asubstrate such as a silicon wafer by a conventional process such as spincoating. The solvent used here is sufficient to dissolve theaforementioned ingredients, have an adequate drying rate, and give auniform and smooth coat after evaporation of the solvent and, hence,solvents generally used in the art can be used. In the presentinvention, the total solid content means total content exclusive ofsolvents.

Examples thereof include glycol ether esters such as ethyl Cellosolveacetate, methyl Cellosolve acetate and propylene glycol monomethyl etheracetate; glycol ethers such as propylene glycol monomethyl ether,di(ethylene glycol) dimethyl ether, esters such as ethyl lactate, butyllactate, amyl lactate and ethyl pyruvate and the like; ketones such asacetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; cyclicesters such as γ-butyrolactone, and the like. These solvents can be usedeach alone or in combination of two or more.

A resist film applied onto the substrate and then dried is subjected toexposure for patterning, then heat-treated for facilitating a deblockingreaction, and thereafter developed with an alkali developer. The alkalideveloper used here may be any one of various alkaline aqueous solutionsused in the art, and generally, an aqueous solution oftetramethylammonium hydroxide or (2-hydroxyethyl)trimethylammoniumhydroxide (commonly known as “choline”) is often used.

It should be construed that embodiments disclosed here are examples inall aspets and not restrictive. It is intended that the scope of thepresent invention is determined not by the above descriptions but byappended Claims, and includes all variations of the equivalent meaningand ranges to the Claims.

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention. The “%” and “part(s)” used to represent the content of anycomponent and the amount of any material used in the following examplesand comparative examples are on a weight basis unless otherwisespecfically noted. The weight-average molecular weight of any materialused in the following examples is a value found by gel permeationchromatography [HLC8120GCP Type, Column (Three Columns): TSKgelMultipore HXL-M, Solvent: Tetrahydrofuran, manufactured by TOSOHCORPORATION] using styrene as a standard reference material. Structuresof compounds were determined by NMR (GX-270 Type, or EX-270 Type,manufactured by JEOL LTD) and mass spectometry (Liquid Chromatography:1100Type, manufactured by Agilient, Mass Spectrometry: LC/MSD Type,manufactured by Agilient).

EXAMPLE 1

(Synthesis of triphenylsulfonium(1-cyclohexylmethoxycarbonyl)difluoromethanesulfonate)

(1) 230 Parts of 30% aqueous sodium hydroxide solution was addeddropwise into a mixtuxe of 100 parts of methyldifluoro(fluorosulfonyl)acetate and 250 parts of ion-exchanged water ina ice bath. The added mixture was heated and refluxed at 100° C. for 25hours. After cooling, the cooled mixture was neutralized with 88 partsof conc. hydrochloric acid and concentrated to obtain 158.4 parts ofsodium difluorosulfoacetate (containing inorganic salt, purity: 65.1%).

(2) 50.0 Parts of sodium difluorosulfoacetate (purity: 65.1%), 18.76parts of cyclohexylmethanol and 377 parts of dichloroethane were chargedin a vessel, 31.26 parts of p-toluenesulfonic acid (p-TsOH) was addedthereto, and the mixture was refluxed for 6 hours. After concentratingthe mixture to eliminate dichloroethane, 200 parts of n-heptane wasadded thereto to wash, and the washing solvent was eliminated byfiltration. The solid obtained by filtration was added with 200 parts ofacetonitrle and the mixture was stirred and filtrated. The filtrate wasconcentrated to obtain 39.03 parts of sodium salt of 1-cyclohexylmethyldifluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 0.90-1.27 (m, 5H); 1.58-1.71 (m, 6H) 4.02 (d,2H)

(3) 39.03 Parts of sodium salt of 1-cyclohexylmethyldifluorosulfoacetate obtained in (2) above was dissolved in 195.2 partsof ion-exchanged water. A solution consisting of 39.64 parts oftriphenylsulfonium chloride and 196.4 parts of ion-exchanged water wasadded to the solution and then 500 parts of acetonitrile was furtheradded thereto. After stirred for 15 hours, the stirred mixture wasconcentrated and extracted with 250 parts of chloroform twice. Theorganic layers were mixed and washed with ion-exchanged water. Theobtained organic layer was concentrated. 200 Parts of tert-butyl methylether was added to the concentrate, and the mixture was stirred,filtered and dried to obtain 40.16 parts of triphenylsulfonium(1-cyclohexylmethoxycarbonyl)difluoromethanesulfonate, which is calledas acid generator B1.

¹H-NMR data of acid generator B1 (dimethylsulfoxide-d₆, InternalStandard: tetramethylsilane): d(ppm) 0.88-1.28 (m, 5H); 1.56-1.71 (m,6H); 4.01 (d, 2H); 7.75-7.90 (m, 15H) MS (ESI(+) Spectrum): M+263.1(C₁₈H₁₅S+=263.09) MS (ESI(−) Spectrum): M-271.1 (C₉H₁₃F₂O₅S⁻=271.05)

EXAMPLE 2

(Synthesis of1-(2-oxo-2-phenylethyl)tetrahydrothiophenium(1-cyclohexylmethoxycarbonyl)difluoromethanesulfonate)

(1) 150 Parts of 2-bromoacetophenone was dissolved in 375 parts ofacetone, and 66.5 parts of tetrahydrothiophene was added dropwisethereto. After the mixture was stirred at room temperature for 24 hours,white solid obtained was filtered, washed with acetone and then dried toobtain 207.9 parts of 1-(2-oxo-2-phenylethyl)tetrahydrothiopheniumbromide in the form of white crystals.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 2.13-2.36 (m, 4H); 3.50-3.67 (m, 4H); 5.41(s, 2H); 7.63 (t, 2H); 7.78 (t, 1H); 8.02 (d, 2H)

(2) 6.00 Parts of sodium salt of 1-cyclohexylmethyl difluorosulfoacetateobtained in Example 1 (2) was dissolved in 60.0 parts of acetonitrile. Asolution consisting of 5.86 parts of1-(2-oxo-2-phenylethyl)tetrahydrothiophenium bromide obtained in (1)above and 58.6 parts of ion-exchanged water was added to the solution.After stirred for 15 hours, the stirred mixture was concentrated andextracted first with 100 parts of and second 50 parts of chloroform. Theorganic layers were mixed and washed with ion-exchanged water. Theobtained organic layer was concentrated. 30 Parts of tert-butyl methylether was added to the concentrate, and the mixture was stirred,filtered and dried in reduced pressure obtain 5.6 parts of1-(2-oxo-2-phenylethyl)tetrahydrothiophenium(1-cyclohexylmethoxycarbon)difluoromethanesulfonate in the form of whitecrystals, which is called as acid generator B2.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 0.88-1.28 (m, 1.56-1.70 (m, 6H); 2.13-2.33(m, 4H); 3.46-3.64 (m, 4H); 4.02(s, 2H); 5.31 (s, 2H); 7.63 (t, 2H)7.78(t, 1H);8.00(d, 2H) MS (ESI(+) Spectrum): M+207.0 (C₁₂H₁₅OS⁺=207.08) MS(ESI(−) Spectrum): M−271.0 (C₉H₁₃F₂O₅S⁻=271.05)

EXAMPLE 3

(Synthesis of triphenylsulfonium(2-norbornanemethoxycarbonyl)difluoromethanesulfonate)

(1) 8.1 Parts of sodium difluorosulfoacetate (purity: 61.9%), 32 partsof 2,norbornanemethanl and 200 parts of dichloroethane were charged in avessel, 4.8 parts of p-toluenesulfonic acid (p-TsOH) was added thereto,and the mixture was refluxed for 7 hours. After concentrating themixture to eliminate dichloroethane, 100 parts of tert-butyl methylether was added thereto to wash, and the washing solvent was eliminatedby filtration. The solid obtained by filtration was added with 100 partsof ethyl acetate and the mixture was stirred and filtrated. The filtratewas concentrated to obtain 5.4 parts of sodium salt of2-norbornanemethyl difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 0.65-0.72 (m, 1H); 1.03-1.78 (m, 7H);2.14-224 (m, 3H); 3.87-4.27 (m, 2H)

(2) 5.4 Parts of sodium salt of 2-norbornanemethyl difluorosulfoacetateobtained in (1) above was dissolved in 54.3 parts of ion-exchangedwater. A solution consisting of 5.3 parts of triphenylsulfonium chlorideand 55 parts of methanol was added to the solution. After stirred for 24hours, the stirred mixture was concentrated and extracted with 54 partsof chloroform twice. The organic layers were mixed and washed withion-exchanged water. The obtained organic layer was concentrated. 54Parts of tert-butyl methyl ether was added to the concentrate, and themixture was stirred, filtered and dried to obtain 8.4 parts oftriphenylsulfonium (2-norbornanemethoxycarbonyl)difluoromethanesulfonatein the form of white solid, which is called as acid generator B3.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 0.64-0.72 (m, 1H), 1.03-1.80 (m, 7H);2.13-2.22 (m, 3H); 3.86-4.26 (m, 2H); 7.75-7.91 (m, 15H) MS (ESI(+)Spectrum); M+263.2 (C₁₈H₁₅S⁺=263.09) MS (ESI(−) Spectrum); M−283.0(C₁₀H₁₃F₂O₅S⁻=283.05)

RESIN SYNTHESIS EXAMPLE 1 Synthesis of Resin A1

2-Ethyl-2-adamantyl methacrylate, 3-hydroxy-1-adamantyl methacrylate andα-methacryloyloxy-γ-butyrolactone were charged at a molar ratio of5:25:25 (20.0 parts:9.5 parts:7.3 parts), and methyl isobutyl ketone intwice weight based on all monomers was added, to prepare solution. Tothe solution was added azobisisobutyronitrile as an initiator in a ratioof 2 mol % based on all monomer molar amount, and the mixture was heatedat 80° C. for about 8 hours. Then, the reaction solution was poured intolarge amount of heptane to cause precipitation, and this operation wasrepeated three times for purification. As a result, copolymer having aweight-average molecular weight of about 9200 was obtained. This iscalled resin A1.

EXAMPLES 1 TO 2 AND COMPARATIVE EXAMPLE 1

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare resist liquid.

<Resin>

-   resin A1: 10 parts    <Acid Generator>-   acid generator B1: 0.232 part

-   acid generator B3: 0.237 part

-   acid generator C1: 0.244 part-   Triphenylsulfonium perfluorobutanesulfonate    <Quencher>-   quencher Q1: 2,6-diisopropylaniline 0.0325 part    <Solvent>

Solvent Y1: propylene glycol monomethyl ether acetate 80.0 parts2-heptanone 20.0 parts γ-butyrolactone  3.0 parts

Silicon wafers were each coated with “ARC-29A-8”, which is an organicanti-reflective coating composition available from Brewer Co., and thenbaked under the conditions; 215° C., 60 seconds, to form a 780 Å-thickorganic anti-reflective coating. Each of the resist liquids prepared asabove was spin-coated over the anti-reflective coating so that thethickness of the resulting film became 0.25 μm after drying. The siliconwafers thus coated with the respective resist liquids were each prebakedon a direct hotplate at a temperature of 130° C. for 60 seconds. Usingan ArF excimer stepper (“NSR ArF” manufactured by Nikon Corporation,NA=0.55, ⅔ Annular), each wafer thus formed with the respective resistfilm was subjected to line and space pattern exposure, with the exposurequantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature of 130° C. for 60 seconds and then to paddledevelopment for 60 seconds with an aqueous solution of 2.38 wt %tetramethylammonium hydroxide.

Each of a bright field pattern developed on the organic anti-reflectivecoating substrate was observed with a scanning electron microscope, theresults of which are shown in Table 1. The term “bright field pattern”,as used herein, means a pattern obtained by exposure and developmentthrough a reticle comprising an outer frame made of a chromium layer(light-shielding layer) and linear chromium layers (light-shieldinglayers) formed on a glass surface (light-transmitting portion) extendinginside the outer frame. Thus, the bright field pattern is such that,after exposure and development, resist layer surrounding the line andspace pattern is removed while resist layer corresponding to the outerframe is left on the outer side of the region from which the resistlayer is removed.

Effective sensitivity (ES):

It is expressed as the amount of exposure that the line pattern(light-shielding layer) and the space pattern (light-transmitting layer)become 1:1 after exposure through 0.13 μm line and space pattern maskand development.

Resolution:

It is expressed as the minimum size of space pattern which gave thespace pattern split by the line pattern at the exposure amount of theeffective sensitivity.

TABLE 1 No. Acid Generator Resolution (μm) ES (mJ/cm²) Example 1 B1 0.1225.0 Example 2 B3 0.12 27.5 Comparative C1 0.13 22.5 Example 1

Furthermore, the resist patterns obtained from Examples 1 and 2 haveexcellent pattern shape because top side length and bottom side lengthof the patterns are almost the same.

Salt (I) is suitably used for an acid generator capable of providingchemically amplified resist compositions giving patterns having higherresolution and excellent pattern shape and the present resistcomposition is especially suitably used for an acid generator capable ofproviding chemically amplified resist compositions for ArF excimer laserlithography, KrF excimer laser lithography and ArF immersionlithography.

1. A salt of the formula (I):

wherein ring X represents monocyclic or bicyclic hydrocarbon grouphaving 3 to 30 carbon atoms, and one or more hydrogen atom in the ring Xis optionally substituted with alkyl group having 1 to 6 carbon atoms,alkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q¹ andQ² each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and n isan integer of 1 to
 12. 2. The salt according to claim 1, wherein thering X is monovalent residue of a compound shown by the formula (IIIa),(IIIb), (IIIc), (IIId), (IIIe) or ((IIIf):

wherein X¹ represents alkylene group, oxygen atom or sulfur atom, andone or more hydrogen atom in the formulae (IIIa), (IIIb), (IIIc),((IIId), (IIIe) and (IIIf) is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 2 to 6 carbon atoms orperfluoroalkyl group having 1 to 4 carbon atoms, and f is an integer of1 to
 10. 3. The salt according to claim 2, wherein the ring X iscyclohexyl group or bicyclo[2.2.1]heptyl group.
 4. The salt according toclaim 1, wherein A⁺ is at least one cation selected from the groupconsisting of the formula (IIe), the formula (IIb), the formula (IIc)and the formula (IId); a cation of the formula (IIe):

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms, a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl group having 1 to12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P⁶and P⁷ bond to form divalent acyclic hydrocarbon group having 3 to 12carbon atoms which forms a ring together with the adjacent S⁺, and oneor more —CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12carbon atoms or aromatic ring group optionally substituted, or P⁸ and P⁹bond to form divalent acyclic hydrocarbon group which forms2-oxocyloalkyl together with the adjacent —CHCO—, and one or more —CH₂—in the divalent acyclic hydrocarbon group is optionally substituted with—CO—, —O— or —S—, a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹³, P¹⁴, P¹⁵, P¹⁶, P⁷, P¹⁸, P¹⁹, P²⁰ and P²¹ eachindependently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m is an integer 0 or
 1. 5.The salt according to claim 4, wherein the cation of the formula (IIe)is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 30 carbon atoms, and l, k,j, i, h and g each independently is an integer of 0 to
 5. 6. The saltaccording to claim 4, wherein the cation of the formula (IIe) is acation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 7. The salt according to claim 6, whereinthe cation of the formula (IIa) is a cation of the formula (IIi):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 carbon.
 8. The salt according to claim 1,wherein the salt is a salt of the formula (IV) or (V)

P²², P²³ and P²⁴ each independently represents a hydrogen atom or alkylgroup having 1 to 4 carbon atoms.
 9. The salt according to claim 1,wherein each of Q¹ and Q² is independently fluorine atom ortrifluoromethyl group.
 10. A process for producing a salt of the formula(I)

wherein ring X represents monocyclic or bicyclic hydrocarbon grouphaving 3 to 30 carbon atoms, and one or more hydrogen atom in the ring Xis optionally substituted with alkyl group having 1 to 6 carbon atomalkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q¹ andQ² each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ rep resets organic counter ion; and n isan integer of 1 to 12, which comprises reacting an ester compound of theformula (VI)

wherein M represent Li, Na, K or Ag; and n is an integer of 1 to 12, andwherein ring X represents monocyclic or bicyclic hydrocarbon grouphaving 3 to 30 carbon atoms and one or more hydrogen atoms on the ring Xare optionally replaced with alkyl group having 1 to 6 carbon atoms, analkenyl group having 2 to 6 carbon atoms, an alkoxy group having 2 to 6carbon atoms or a perfluoroalkyl group having 1 to 4 carbon atoms; andQ¹ and Q² each independently represents a fluorine atom orperfluoroalkyl group having 1 to 6 carbon atoms with a compound of theformula (IX)A⁺ Z⁻  (IX) wherein Z represents F, Cl, Br, I, BF₄, AsF₆, PF₆ or ClO₄,and A⁺ represents an organic counter ion.
 11. A chemically amplifiedresist composition comprising a salt of the formula (I)

wherein ring X represents monocyclic or bicyclic hydrocarbon grouphaving 3 to 30 carbon atoms, and one or more hydrogen atom in the ring Xis optionally substituted with alkyl group having 1 to 6 carbon atoms,alkenyl group having 2 to 6 carbon atoms, alkoxy group having 2 to 6carbon atoms or perfluoroalkyl group having 1 to 4 carbon atoms; Q¹ andQ² each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and n isan integer of 1 to 19, and a resin which contains a structural unithaving an acid-labile group and which itself is insoluble or poorlysoluble in an alkali aqueous solution but becomes soluble in an alkaliaqueous solution by the action of an acid.
 12. The composition accordingto claim 11, wherein the resin contains a structural unit derived from amonomer having a bulky and acid-labile group.
 13. The compositionaccording to claim 12, wherein the bulky and acid-labile group is2-alkyl-2-adamantyl group or 1-(1-adamantyl)-1-alkylalkyl group.
 14. Thecomposition according to claim 12, wherein the monomer having bulky andacid-labile group is 2-alkyl-2-adamantyl (meth)acrylate,1-(1-adamantyl-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl5-norbornene-2-carboxylate, 1-(-1-adamantyl)-1-alkylalkyl5-norbornene-2-carboxylate 2-alkyl-2-adamantyl α-chloroacrylate or1-1-(adamantyl)-1-alkylalkyl α-chloroacrylate.
 15. The compositionaccording to claim 11, wherein the composition further comprises a basiccompound.
 16. The composition according to claim 11, wherein each of Q¹and Q² is independently fluorine atom or trifluoromethyl group.
 17. Thecomposition according to claim 11, wherein the ring X is monovalentresidue of a compound shown by the formula (IIIa), (IIIb), (IIIc),((IIId), (IIIe) or (IIIf):

wherein X¹ represents alkylene group, oxygen atom or sulfur atom, andone or more hydrogen atom in the formulae (IIIa), (IIIb), (IIIc),((IIId), (IIIe) and (IIIf) is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 2 to 6 carbon atoms orperfluoroalkyl group having 1 to 4 carbon atoms, and f is an integer of1 to
 10. 18. The composition according to claim 11, wherein the ring Xis cyclohexyl group or bicyclo[2.2.1]heptyl group.
 19. The compositionaccording to claim 11, wherein A⁺ is at least one cation selected fromthe group consisting of the formula (IIe), the formula (IIb), theformula (IIc) and the formula (IId); a cation of the formula (IIe):

wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group having1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb):

wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms, a cation of the formula (IIc):

wherein P⁶ and P⁷ each independently represent alkyl group having 1 to12 carbon atoms or cycloalkyl group having 3 to 12 carbon atoms, or P⁶and P⁷ bond to form divalent acyclic hydrocarbon group having 3 to 12carbon atoms which forms a ring together with the adjacent S⁺, and oneor more —CH₇— in the divalent acyclic hydrocarbon group is optionallysubstituted with —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl group having 1 to 12 carbon atoms, cycloalkyl group having 3 to 12carbon atoms or aromatic ring group optionally substituted, or P⁸ and P⁹bond to form divalent acyclic hydrocarbon group which forms2-oxocycloalkyl together with the adjacent —CHCO—, and one or more —CH₂—in the divalent acyclic hydrocarbon group is optionally substituted with—CO—, —O— or —S—, a cation of the formula (IId):

wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atomsB represents sulfur atom or oxygen atom, and m is an integer of 0 or 1.20. The composition according to claim 19, wherein the cation of theformula (IIe) is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 carbonatoms except phenyl group, wherein one or more hydrogen atom in thealkyl group is optionally substituted with hydroxyl group, alkoxy grouphaving 1 to 12 carbon atoms or cyclic hydrocarbon group having 3 to 12carbon atoms and wherein one or more hydrogen atom in the cyclichydrocarbon group is optionally substituted with hydroxyl group, alkylgroup having 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbonatoms; and P³¹, P³² P³³, P³⁴, P³⁵ and P³⁶ each independently representhydoxyl group, alkyl group having 1 to 12 carbon atoms, alkoxy grouphaving 1 to 12 carbon atoms or cyclic hydrocarbon group having 3 to 12carbon atoms, and l, k, j, i, h and g each independently show an integerof 0 to
 5. 21. The composition according to claim 19, wherein the cationof the formula (IIe) is a cation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 22. The composition according to claim 21,wherein the cation of the formula (IIa) is a cation of the formula(IIi):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 carbon.
 23. The composition according to claim12, wherein the salt is a salt of the formula (IV) or (V)

P²², P²³ and P²⁴ each independently represent a hydrogen atom or analkyl group having 1 to 4 carbon atoms.